Semi-conductive device



Feb. 18, 1958 ODELL 2,824,268 I SEMI-CONDUCTIYE DEVICE Filed Oct. 21, 1953 FIG.I

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HIS AGENT United States Patent Patented Feb. 18, 1958 SEMI-CONDUCTIVE DEVICE Newton H. Odell, Bethlehem, Pa., assignor, by mesne assignments, to General Dynamics Corporation, a corporation of Delaware Application October 21, 1953, Serial No. 387,377

7 Claims. (Cl. 317-235) My invention relates to semi-conductive devices, or transistors, and more particularly to semi-conductive devices of the point-contact type.

Semi-conductive devices of the point-contact type generally comprise a body of semi-conductive material in contact with which are first, second and third electrodes. The first electrode usually comprises a plate or other relatively flat surface which bears on a similarly flat surface on the body of semi-conductive material. This electrode, which is usually called the base, may be said to have area-contact characteristics relative to the body.

The second and third electrodes prior to my invention have comprised a pair of cat-whiskers bearing on the body of semi-conductive material, usually on a surface of the body opposite to the base-contact surface. One of these electrodes is known as the emitter, the other as the collector. The area of contact between the second and third electrodes on one hand and the body of semi-conductive material on the other hand is minimized insofar as possible, and these electrodes may be said to have point-contact characteristics relative to the body.

Conventional point-contact transistors prior to my invention are most closely analogous, insofar as analogies can be drawn, to a three-element vacuum tube whose grid has uniform spacing of wire, and which therefore exhibits sharp cutoif characteristics. Insofar as I am aware, a transistor action similarly analogous to that of a variable-mu vacuum tube, that is, with remote cut-off characteristics, has not been achieved before my invention.

It is an object of my invention to provide a new and improved semi-conductive device of the point-contact type.

It is another object of my invention to provide a semiconductive device of the point-contact type having remote cutoff characteristics.

In general I accomplish these and other objects of my invention by using a third, or collector, electrode having line-contact characteristics relative to the body of semi-conductive material, rather than the point-contact characteristics used heretofore.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing in which:

Fig. l is a top view of one embodiment of my invention;

Fig. 2 is a section, taken through line 2-2 in Fig. 1; and

Fig. 3 is a section similar to that shown in Fig. 2 of another embodiment of my invention.

Referring now to Figs. 1 and 2, there is shown a body 1 of semi-conductive material in contact with which is a first, or base, electrode 2. Conductor 3 may be attached by any convenient means to base 2, such as by soldering 4. Conductor 3 may be used to connect the base electrode to the circuit in which the transistor is to be employed.

Preferably placed in contact against an upper plane surface 5 of the semi-conductive material as shown are pointed end 6 of a cat-whisker emitter electrode 7, and knife contact 8 of a collector electrode 9. Contact 8 preferably has a circular shape; that is, the figure formed at the contact between 8 and body 1 is preferably a circle, as indicated. Furthermore, contact 8 is preferably eccentrically located with respect to the second, or emitter, electrode 7 Electrode 7 may be held in position relative to eletrode 9' by means of an insulating support 10, a drive fit preferably being used between electrode 7 and insulator it) and also between insulator 1t) and the inside of collector electrode Conductors 11 and 12, respectively soldered at points 13 and 14 to electrodes 7 and 9, may be used to connect these electrodes to the circuit in which the semi-conductive device is to be used.

The entire assembly may be housed in an insulating container l5, and spring '16 extending between the inside bottom surface 17 of container 15 and the lower surface 18 of base electrode 2, may be used to keep the electrodes firmly in contact with body 1 of semi-conductive material. A press fit between collector electrode 9 and the inner wall of housing 15 may be used to maintain the parts in compression.

The embodiment of my invention shown in Figs. l and 2 may be employed in conventional point-contact transistor circuit configurations. The characteristic curves achieved, however, are different in that a remote cutoff point is achieved. This action I attribute to the fact that some portion of contact 8 of the third, or collector, electrode 9 are closer to point contact 6 of electrode 7 than are other portions of the contact part 8 of electrode 9. By closer, I mean closer as measured over the surface 5 of the body 1 of semi-conductive material.

As is well known, conduction in conventional two-catwhisker semi-conductive devices reaches saturation when all the holes that are available reach the collector electrode. With my invention, however, saturation occurs sooner for some portions of the contact part of electrode 9 than for others. in other words, the semi-conductive material between contact 6 and the nearest portion of contact it saturates first, followed by the increasingly distant portions until the farthermost portion is reached. The remote cutoff action mentioned above is thereby achieved.

Those skilled in the art can readily appreciate that shapes other than circular may be employed according to my invention for the line-contact part of electrode 9, as may appear advantageous for various applications; for example, ellipsoidal or other curved shapes may prove advantageous. Such shapes are most easily achieved, of course, by making electrode with the desired curve and then forming the desired type of lower end thereon. It should be noted that even a straight shape is capable of giving the remote-cutoff characteristic of my invention.

It can further be appreciated that a knife edge is not the only cross-sectional configuration for the lower end of electrode 9. Fig. 3 shows a moification in which electrode 9 has a blunt lower end. As can be observed, however, as far as conduction between electrodes is concerned, the inner edge 19 of electrode 9 in Fig. 3 produces substantially the same effect as knife edge 8 in Fig. 2. I prefer to employ the words edged characteristics to describe the nature of knife 8, corner 19 and similar configurations which behave in like manner as far as transistor action isconcerned. This definition of necessity includes a rounded lower end for electrode 9, .of course, because there is an edged characteristic where the rounded lower end meets the. body of semiconductive material.

While I have shown and described my invention as applied to specific embodiments thereof, still other modifications will readily occur to those skilled in the art. I do not, therefore, desire my invention to be limited to the specific arrangements shown and described, and I. intend in the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim is:

1. In a semi-conductive device, the combination of a body of semi-conductive material and first, second and third electrodes, each in contact with said body; said first electrode having area-contact characteristics relative to said body; said second electrode having substantially point-contact characteristics relative to said body; and said third electrode having a contact part having line-contact characteristics relative to said body, the con tact part of said third electrode being oriented on said body such that some portions of said contact part are closer, measured over the surface of said body, to said second electrode than other portions of said contact part.

2. A combination of claim 1 in which said contact part of said third electrode has edged characteristics.

3. The combination of claim 1 in which said contact part has a curved shape.

4. The combination of claim 1 in which said contact part is a circle eccentrically located around said second electrode.

5. In a semi-conductive device, the combination of a body-of semi conductive material and first, second and third electrodes; said first electrode having a relatively extended area of contact with said body of semi-conductive material; said second electrode having a pointcontact with said body; and said third electrode having an extended circular line-contact with said body, the circular line-contact being eccentric with respect to the pointcontact of said'second electrode.

6. In a semi-conductive device, the combination of a body of semi-conductive material, a first electrode having a point-contact with said body, anda second electrode having line-contact with said body, the line-contact being asymmetrically disposed with respect to said point-contact so that electric fields along said line, caused by voltages at said point, are nonuniform.

7. In combination, a semi-conductive body; a first, a second and a third electrode contacting said body; the relative sizes of the junctions of said first, second and third electrodes with said body being, respectively, an extended area, an elongated narrow line, and a point; said second and third electrodes being so disposed that said point is unequal distances from different portions of said line.

References Cited in the file of this patent UNITED STATES PATENTS 2,563,503 Wallace Aug. 7, 1951 2,672,580 Henderson et al Mar. 16, 1954 2,717,341 North Sept. 6, 1955 

